System for learning the fullyclosed opening degree of subsidiary throttle valve

Abstract: In a system for learning the fully-closed opening degree of a subsidiary throttle valve, if a stable state judging means judges that a state in which an influence is not exerted to the operational state of the engine (a state in which the vehicle is stopped and the engine is in an idling state) even if the subsidiary throttle valve is fully closed, a valve closing means closes the subsidiary throttle valve and a fully-closed opening degree learning means starts learning. If the opening degree of the subsidiary throttle valve or the engine revolution number is largely varied during the learning of the fully-closed opening degree learning means, a valve-closing prohibiting means prohibit the closing of the subsidiary throttle valve to discontinue the learning. Even if all of the conditions for learning are satisfied again, the closing of the subsidiary throttle valve and learning by the fully-closed opening degree learning means are prohibited until the comparator circuit judges that the vehicle starts traveling and vehicle speed exceeds a reference value.

Description: BACKGROUND OF THE INVENTION FIELD OF THE INVENTION The present invention relates to a system for learning in use the fully-closed opening degree of a subsidiary throttle valve disposed in series with a main throttle valve mounted in an intake passage in an engine. DESCRIPTION OF THE PRIOR ART For example, in an engine of a vehicle including a traction control device, a main throttle valve connected to an accelerator pedal and opened and closed by the accelerator pedal, and a subsidiary throttle valve connected to an actuator and opened and closed by the actuator are mounted in series. And when an excessive slipping of a driven wheel occurs, the subsidiary throttle valve is controlled to be closed, thereby reducing the output from the engine to suppress the excessive slipping. To accurately control the opening degree of the subsidiary throttle valve, it is necessary to correctly detect the opening degree of the subsidiary throttle valve. For this purpose, a system for learning the fully-opened opening degree of the subsidiary throttle valve has been proposed (see Japanese Patent Application Laid-open No.107926/81). This prior art system is designed such that when the actuator for opening and closing the subsidiary throttle valve is in a non-energized state and the subsidiary throttle valve is in a fully opened state, the fully opened degree is learned by detecting it by a sensor and storing it. The subsidiary throttle valve is normally in an opened state and is closed when the traction control device is operated. However, the important opening degree of the subsidiary throttle valve for suppressing the excessive slipping of the driven wheel, is near a substantially fully-closed opening degree. For this reason, the system for learning the fully-closed opening degree of the subsidiary throttle valve as in the prior art is accompanied by a problem that it is impossible to carry out an effective learning. In order to avoid such disadvantage, it may be conceived that the fully-closed opening degree of the subsidiary throttle valve should be learned. However, if the subsidiary throttle valve is closed into a fully-closed state, an influence is exerted to the operational state of the engine and hence, it is necessary to learn the fully-closed opening degree while selecting a particular operational state (e.g., an idling state) in which such influence is minimized. However, even if all of a plurality of conditions in which the engine is in the above-described particular operational state are satisfied and the subsidiary throttle valve is closed to conduct the learning, the closing of the subsidiary throttle valve must be discontinued once whenever any of these conditions not satisfied. And when all of the conditions are satisfied again, the closing of the subsidiary throttle valve is carried out again. Consequently, the actuator for opening and closing the subsidiary throttle valve is intermittently driven, resulting in disadvantages such as generation of a noise, an increase in consumed electric power and the like. From WO 90/11442 there is known a process for determining an end position of an adjusting device for adjusting a throttle valve. Upon starting an engine an end position of a throttle valve is determined by checking whether a control value has reached a predetermined threshold value. In case the predetermined threshold value has been reached it is determined whether the valve has reached its lower end position. If again the answer is yes, then it is determined whether in the particular moment the throttle valve is controlled into the end position. If all these three conditions have been satisfied, a current position is stored as the lower end position. This procedure can only be carried out during starting the engine, as, during a normal operating condition, closing the valve for determining its end position would adversely influence the running behavior of the engine. From US-PS-5,151,861 there is known a method for controlling an engine output by controlling an opening of a subthrottle valve disposed in an intake part of the engine. US-PS-4,359,894 discloses a system fcr sensing a throttle valve's most close position. The system includes a throttle position sensor and a decision circuit for deciding that the throttle valve position is the most close position in dependence on the magnitude of the signal output by the sensor. From US-PS-4,995,364 there is known a control apparatus for an engine comprising a main throttle and a subthrottle valve mounted in series in an intake port of the engine. In case a deviation between a predetermined opening degree of the throttle valve and an actual opening degree of the main throttle valve is detected, a control of a subthrottle valve is started in order to reliably effect the throttle opening control. It is the object of the present invention to provide a system for learning in use the fully closed opening degree of a subsidiary throttle valve accurately without influencing the running behavior of the engine. According to the present invention, this object is solved by the systems as defined in independent claims 1 and 2. With the arrangement of claim 1, if it is decided that the engine is in a stable operational state in which the engine is stably running which operational state is not varied even if the subsidiary throttle valve is driven into a fully closed state, the subsidiary throttle valve is driven into a fully closed state. When the variation in opening degree of the subsidiary throttle valve is smaller than the predetermined value in such state, when the variation in number of revolutions of the engine is smaller than the predetermined value, or when the purging of the fuel from the canister is stopped, the fully-closed opening degree of the subsidiary throttle valve is learned. Therefore, when the operational state of the engine is suitable for the learning, the learning can be carried out without influencing the operational state of the engine. Moreover, by learning the opening degree of the subsidiary throttle valve which is in the fully closed state, it is possible to accurately control the opening degree of the subsidiary throttle valve near the fully-closed opening degree, which is important for controlling the output of the engine. With the arrangement of claim 2, if it is decided that the engine is in a stable operational state in which the engine is stably running which operationl state is not varied even if the subsidiary throttle valve is driven into a fully closed state, the subsidiary throttle valve is driven into a fully closed state to conduct the learning of the fully-closed opening degree of the subsidiary throttle valve. When the learning is discontinued before completion thereof, the closing of the subsidiary throttle valve is prohibited until the vehicle speed exceeds the predetermined value. Therefore, it is possible to prevent the continuous opening and closing runs of the subsidiary throttle valve to inhibit the generation of a noise and an increase in consumed power. The above and other objects and advantages of the invention will be apparent from the following description of preferred embodiments taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS Fig.1 is a schematic illustration of an arrangement of a vehicle including a fully-closed opening degree learning system for a subsidiary throttle valve; Fig.2 is a block diagram of the fully-closed opening degree learning system for the subsidiary throttle valve; and Fig.3 is a diagram for explaining the operation. DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be described by way of preferred embodiments in connection with the accompanying drawings. Figs.1 to 3 illustrate a first embodiment of the present invention. Fig.1 is a schematic illustration of an arrangement of a vehicle including a fully-closed opening degree learning system for a subsidiary throttle valve; Fig.2 is a block diagram of the fully-closed opening degree learning system for the subsidiary throttle valve; and Fig.3 is a diagram for explaining the operation. As shown in Fig.1, provided in series in an intake passage 1 of an engine E carried on a vehicle are a main throttle valve 3 connected to and opened and closed by an accelerator pedal 2, and a subsidiary throttle valve 5 connected to and opened and closed by an actuator 4 such as a pulse motor or the like. A main throttle valve opening-degree sensor 6 is provided on the main throttle valve 3, and a subsidiary throttle valve opening-degree sensor 7 is provided on the subsidiary throttle valve 5. The main throttle valve opening-degree sensor 6 detects an opening degree of the main throttle valve in terms of a voltage value and outputs an A/D conversion value of the detected voltage value. The subsidiary throttle valve opening-degree sensor 7 detects an opening degree of the subsidiary throttle valve in terms of a voltage value and outputs an A/D conversion value of the detected voltage value. The vehicle includes a pair of left and right driven wheels Wr, Wr driven from the engine E and a pair of left and right follower wheels Wf, Wf. Vehicle speed sensors 8, 8 are provided on the follower wheels Wf, Wf for detecting a vehicle speed Vv from the number of revolutions of the follower wheels Wf, Wf, respectively. An engine revolution-number sensor 9 is provided on the engine E for detecting the number of revolutions of the engine E, and a brake switch 11 is provided on the brake pedal 10 for detecting the operation of the brake pedal 10. Outputs from the main throttle valve opening-degree sensor 6, the subsidiary throttle valve opening-degree sensor 7, the vehicle speed sensors 8, 8, the engine revolution-number sensor 9 and the brake switch 11 are supplied to an electronic control unit U, where a zero-point correction is carried out by learning the fully-closed opening degree of the subsidiary throttle valve opening-degree sensor 7. More specifically, it is possible to accurately detect an actual opening degree of the subsidiary throttle valve 5 by learning an output value from the subsidiary throttle valve opening-degree sensor 7 when the subsidiary throttle valve 5 is in its fully closed state, and by subtracting the learned value as a zero-point correction value from the output value from the subsidiary throttle valve opening-degree sensor 7. A procedure for determining the zero-point correction value will be described below in detail. Fig.2 illustrates the arrangement of a circuit in the electronic control unit U. An output value TH1 (an A/D conversion value) from the main throttle valve opening-degree sensor 6 is supplied to a main throttle opening-degree judging means 21, where the output value TH1 is compared with a reference value. If the output value TH1 is equal to or less than the reference value, i.e., if the main throttle valve 3 is in a substantially fully closed position, then an output from the main throttle opening-degree judging means 21 is of a high level. An output value TH2 (an A/D conversion value) from the subsidiary throttle valve opening-degree sensor 7 is supplied to a subsidiary throttle opening-degree judging means 22. If the output value TH2 is within a predetermined acceptable range and does not indicate an abnormal value, then an output from the subsidiary throttle opening-degree judging means 22 is of a high level. The vehicle speed Vv delivered by the vehicle speed sensors 8, 8 is supplied to a vehicle speed judging means 23. If it is decided in the vehicle speed judging means 23 that the vehicle speed Vv is 0 (i.e., the vehicle is in a stopped state), an output from the vehicle speed judging means 23 is brought into a high level. An engine-revolution number Ne delivered by the engine-revolution number sensor 9 is supplied to an engine-revolution number judging means 24. If it is decided in the engine-revolution number judging means 24 that the engine-revolution number Ne is, for example, within a range of 600 to 700 rpm, and the engine E is in an idling state, then an output from the engine-revolution number judging means 24 is of a high level. When the brake pedal 10 is depressed to turn ON the brake switch 11, an output from a brake judging means 25 is brought into a high level. The outputs from the main throttle opening-degree judging means 21, the subsidiary throttle opening-degree judging means 22, the vehicle speed judging means 23, the engine-revolution number judging means 24 and the brake judging means 25 are supplied to an AND circuit 26. An output from the AND circuit 26 is brought into a high level, if all of the outputs from the judging means 21 to 25 are of high levels, i.e., if the brake pedal 10 has been depressed so that the vehicle is in its stopped state, and the main throttle valve 3 has been closed into the substantially fully closed state, so that the engine E is in its idling state, and it is decided that the output from the subsidiary throttle valve opening-degree sensor 7 is normal and as a result, even if the subsidiary throttle valve 5 is closed, the operational state of the engine E is not influenced in any way. The main throttle opening-degree judging means 21, the subsidiary throttle opening-degree judging means 22, the vehicle speed judging means 23, the engine-revolution number judging means 24, the brake judging means 25 and the AND circuit 26 constitute a stable-state judging means 27 of the present invention. The output from the AND circuit 26 is supplied through a NOT circuit 28 to an OR circuit 29. Further, an output from a subsidiary throttle valve opening-degree variation judging means 30 which will be described hereinafter is supplied through an NOT circuit 31 to the OR circuit 29. And an output from an engine revolution-number variation judging means 32 which will be described hereinafter is supplied through a NOT circuit 33 to the OR circuit 29. Thus, if it is decided that the operational state of the engine is influenced when the output from the stable-state judging means 27 is of a low level and the subsidiary throttle valve 5 is closed, or if the output from the subsidiary throttle valve opening-degree variation judging means 30 is of a low level, thereby indicating that the opening degree TH2 of the subsidiary throttle valve has been varied, or if the output from the engine revolution-number variation judging means 32 is of a low level, thereby indicating that the engine revolution-number Ne has been varied, an output from the OR circuit 29 is brought into a high level. If the output from the OR circuit 29 has reached the high level, an output from a valve-closing inhibiting means 35 is brought into a high level to prohibit the closing of the subsidiary throttle valve 5. The output from the valve-closing inhibiting means 35 is supplied through a NOT circuit 37 to an AND circuit 36 connected to the stable-state judging means 27. Thus, if it is decided that the output from the stable-state judging means 27 is of a high level and the operational state of the engine E is not influenced even if the subsidiary throttle valve 5 is closed, and if it is decided that the output from the valve-closing prohibiting means is of a low level and it is not necessary to prohibit the closing of the subsidiary throttle valve 5, an output from the AND circuit 36 is brought into a high level. When the output from the AND circuit 36 has reached the high level, a valve closing means 38 closes the subsidiary throttle valve 5 toward a fully closed position through the actuator 4. The closing of the subsidiary throttle valve 5 is achieved by closing it through a predetermined angle (e.g., 2 ° ) for every loop. When the output from the AND circuit 36 has reached the high level, a timer 39 starts counting. After the subsidiary throttle valve 5 become fully closed after a lapse of a predetermined time, the opening degree TH2 of the subsidiary throttle valve 5 is sampled in a subsidiary throttle valve opening-degree sampling means 40 for every loop, until a further predetermined time is lapsed. If the timer has reached a time-up to complete a predetermined number of samplings, a valve-opening means 41 opens the subsidiary throttle valve 5 toward an original position through the actuator 4. A subsidiary throttle valve opening-degree average value calculating means 42 calculates an average value from a plurality of opening degrees TH2 of the subsidiary throttle valve 5 in the sampled and fully closed state, and a zero-point correction value calculating means 43 calculates a zero-point correction value DTH2 by subtracting the average value from the reference value of the fully-closed opening degree. Thus, the zero-point correction of the subsidiary throttle valve opening-degree sensor 7 can be performed by using, as an opening degree of the subsidiary throttle valve 5, a value resulting from the subtraction of the zero-point correction value DTH2 from the output value TH2 (A/D conversion value) from the subsidiary throttle valve opening-degree sensor 7. The subsidiary throttle valve opening-degree sampling means 40, the subsidiary throttle valve opening-degree average value calculating means 42 and the zero-point correction value calculating means 43 constitute a fully-closed opening degree learning means 44 of the present invention. Thus, it is possible to perform an accurate control of the opening degree near the substantially fully-closed opening degree for the subsidiary throttle valve 5, which is important for the control of an output from the engine E, by conducting the zero-point correction by learning the subsidiary throttle valve opening degree TH2 when the subsidiary throttle valve 5 is in the fully closed state. The AND circuit 36 is connected to a set terminal of the subsidiary throttle valve opening-degree variation judging means 30 to which a signal from the subsidiary throttle valve opening-degree sensor 7 is applied. When a signal from the AND circuit 36 is applied to such set terminal simultaneously with the start of the closing of the subsidiary throttle valve 5, the monitoring of a variation range for the subsidiary throttle valve opening degree TH2 is started. If this variation range is equal to or less than a predetermined value, an output from the subsidiary throttle valve opening-degree variation judging means 30 is brought into a high level. The AND circuit 36 is also connected to a set terminal of the engine revolution-number variation judging means 32 to which a signal from the engine revolution-number sensor 9 is simultaneously applied. When the signal from the AND circuit 36 is applied to such set terminal simultaneously with the start of the closing of the subsidiary throttle valve 5, the monitoring of a variation range for the engine-revolution number is started. If this variation range is equal to or less than a predetermined value, an output from the engine revolution-number variation judging means 32 is brought into a high level. The outputs from the subsidiary throttle valve opening-degree variation judging means 30 and the engine revolution-number variation judging means 32 are supplied through the corresponding NOT circuits 31 and 33 to the OR circuit 29. If the variation in the subsidiary throttle valve opening degree TH2 is large, or if the variation in engine revolution-number Ne is large, then the closing of the subsidiary throttle valve 5 is discontinued. Now, if the output from the stable-state judging means 27 is brought into a low level, or if the output from the subsidiary throttle valve opening-degree variation judging means 30 or the engine revolution-number variation judging means 32 is brought into a low level, a high level output from the OR circuit 29 is applied to a set terminal of the valve-closing prohibiting means 35 comprised of a flip-flop circuit. If an output from the valve-closing prohibiting means 35 is brought into a high level, the learning of the fully-closed opening degree for the subsidiary throttle valve 5 is discontinued. Thereafter, even if the outputs from the stable-state judging means 27, the subsidiary throttle valve opening-degree variation judging means 30 or the engine revolution-number variation judging means 32 is restored to the high level, the output from the valve-closing prohibiting means 35 is maintained at the high level until a signal is supplied to a reset terminal thereof, and the learning once discontinued is not restarted. However, the vehicle speed Vv from the vehicle speed sensors 8, 8 is supplied to a non-inverted terminal of the comparator circuit 45 connected to the reset terminal of the valve-closing prohibiting means 35, and a predetermined reference value V REF has been inputted to an inverted terminal of the valve-closing prohibiting means 35. If the vehicle speed Vv exceeds the reference value V REF and a high level signal is applied to the reset terminal, the output from the valve-closing prohibiting means 35 is reset at a low level, thereby starting the learning. If the learning is once discontinued, the learning is not restarted until the vehicle speed Vv exceeds the reference value V REF . If learning conditions are met after the vehicle speed Vv has exceeded the reference value V REF , the learning is restarted. This will be further described with reference to Fig.3. Even if all of the learning conditions have been satisfied during stoppage of the vehicle and the subsidiary valve has been closed to learn the fully closed opening degree, the subsidiary throttle valve 5 is opened whenever any of the learning conditions are dissatisfied before completion of the learning. Provided that the subsidiary throttle valve 5 is thereafter closed to restart the learning when all of the learning conditions are satisfied again, a plurality of opening and closing runs of the subsidiary throttle valve 5 may be continuously repeated, as shown in Fig.3A. If the opening and closing runs of the subsidiary throttle valve 5 are repeated in this manner, not only an influence is exerted to the control of the engine E, but also problems are arisen such as the generation of a noise, an increase in power consumption and the like. According to the present invention, however, if the learning conditions are dissatisfied before completion of the learning, as shown in Fig.3B, the vehicle is stopped again after the vehicle speed Vv once exceeds the reference value V REF , and the learning is restarted until the learning conditions are satisfied, i.e., only one run of the learning is conducted for every one run of stoppage of the vehicle. Thus, it is possible to obviate the continuously opening and closing movements of the subsidiary throttle valve 5. In the embodiment, the variation in engine revolution-number Ne is monitored by the engine revolution-number variation judging means 32. If the variation is small, the learning is conducted. If the variation is large, the learning is discontinued. In place of direct monitoring of the engine revolution-number Ne, the purging of a canister for adsorbing a fuel evaporated from a fuel tank may be monitored. Specifically, if the evaporated fuel is being purged from the canister into the intake passage 1 in the engine E, the air-fuel ratio is liable to be varied to vary the engine revolution-number Ne. For this reason, the learning may be conducted during suspension of the purging, and may be discontinued during execution of the purging.

Claims: A system for learning in use the fully-closed opening degree of a subsidiary throttle valve (5) disposed in series with respect to a main throttle valve (3) mounted in an intake passage (1) of an engine (E), comprising: A) a valve closing means (38) for closing the subsidiary throttle valve (5), B) a fully-closed opening degree learning means (44) for learning the fully-closed opening degree of the subsidiary throttle valve (5), C) a fully-closed opening degree learning procedure activating means (30, 32) for activating a fully-closed opening degree learning procedure of said fully-closed opening degree learning means (44), further comprising: D) a stable state judging means (27) for judging that the engine (E) is in a stable operational state in which the engine is stably running, which operational state is not varied even if the subsidiary throttle valve (5) is driven into a fully-closed state, said valve closing means (38) closing said subsidiary valve (5) in accordance with an output from said stable state judging means (27), said fully-closed opening degree learning procedure activating means (30, 32) comprising: a) an opening-degree variation judging means (30) for judging that the variation in opening degree of the subsidiary throttle valve (5) is smaller than a predetermined value by monitoring the opening degree of the subsidiary throttle valve (5) after judgment of the stable state of the engine (E) by the stable state judging means (27), and/or one of b) a revolution-number variation judging means for judging that the variation in number of revolutions of the engine is smaller than a predetermined value by monitoring the number of revolutions of the engine (E) after judgment of the stable state of the engine (E) by the stable state judging means (27), and c) a fuel purge judging means for judging the stoppage of purging of fuel by monitoring the purging of fuel from a canister after judgment of the stable state of the engine by the stable state judging means (27). A system for learning in use the fully-closed opening degree of a subsidiary throttle valve (5) disposed in series with respect to a main throttle valve (3) mounted in an intake passage (1) of an engine (E), comprising: A) a valve closing means (38) for closing the subsidiary throttle valve (5), B) a fully-closed opening degree learning means (44) for learning the fully-closed opening degree of the subsidiary throttle valve (5) when the subsidiary throttle valve (5) is fully closed by the valve closing means (38), further comprising: C) a stable state judging means (27) for judging that the engine is in a stable operational state in which the engine is stably running, which operational state is not varied even if the subsidiary throttle valve (5) is driven into a fully closed state, said valve closing-means (38) closing said subsidiary throttle valve (5) in accordance with an output from the stable state judging means (27), D) a valve-closing prohibiting means (35) for prohibiting the operation of the valve-closing means (38) until the vehicle speed (Vv) exceeds a predetermined value (V REF ) , when the stable state judging means (27) states the operational state of the engine (E) as being not stable.

Inventors: IKEDA TORU, NISHIHARA TAKASHI, SHIRAISHI SHUJI, YANO OSAMU, IKEDA, TORU, NISHIHARA, TAKASHI, SHIRAISHI, SHUJI, YANO, OSAMU, IKEDA, TORU, K.K. HONDA GIJUTSU KENKYUSHO, NISHIHARA, TAKASHI, K.K. HONDA GIJUTSU KENKYUSHO, Shiraishi, Shuji, K.K. Honda Gijutsu Kenkyusho, Yano, Osamu, Kabushiki Kaisha PSG
Applicants: HONDA MOTOR CO LTD, HONDA GIKEN KOGYO KABUSHIKI KAISHA
Application year: 1994
Main classification: F02D41
IPC codes: F02D11, F02D41, F02D45, F02D9